High-resolution quantum dot photoresist for Micro LED color conversion layer, preparation method of high-resolution quantum dot photoresist and full-color Micro LED display chip

Abstract

The invention relates to the field of materials, and discloses a high-resolution quantum dot photoresist for a Micro LED color conversion layer, a preparation method of the high-resolution quantum dot photoresist and a full-color Micro LED display chip, preparation raw materials of the quantum dot photoresist comprise a functional component and an optional solvent, based on the total amount of the preparation raw materials, the amount of the functional component is 20-100 wt.%, and the amount of the solvent is 20-100 wt.%. The functional component comprises quantum dots, a polyfunctional monomer, a monofunctional monomer, a coupling agent, an initiator, a leveling agent, a thickening agent and a tackifier. According to the invention, a polyfunctional monomer molecule with an alkyl chain with a certain length is selected as a main body which is triggered to be crosslinked in a photosensitive system, and then a specific monofunctional molecule is added and doped, so that a peeling phenomenon caused by excessive shrinkage in an exposure process and a post-baking process can be effectively prevented.

Description

Technical Field

[0001] This invention relates to the field of materials, specifically to a high-resolution quantum dot photoresist for a color conversion layer in MicroLEDs, its preparation method, and a full-color MicroLED display chip. Background Technology

[0002] Future AR (Augmented Reality) and VR (Virtual Reality) glasses will require ultra-high resolution (≥3000ppi) display optical engines, simultaneously meeting requirements such as ultra-high resolution, low power consumption, high collimation emission, and small size. Micro-LED technology involves miniaturizing, matrixing, and thinning LED chips. However, when the pixel size of Micro LEDs is reduced to below 10 μm, the red / red luminous efficiency drops sharply, leading to poor display quality and increased power consumption. Quantum dots (QDs) are a new type of luminescent material with high luminous efficiency and narrow peak width, enabling low power consumption, high collimation emission, and small size. Utilizing the characteristic of QDs to absorb blue light and efficiently emit red / red light, QD materials can be combined with blue Micro LEDs to achieve full-color displays, namely QDCC Micro LEDs.

[0003] This places certain technical requirements on the QD layer: size matching for Micro LED patterning, blue light absorption rate, high color conversion efficiency, and high stability. Among these, the blue light absorption rate of the QD layer is the most critical factor. High blue light absorption rate can reduce the thickness of the QD layer, thereby improving patterning accuracy, reducing optical crosstalk, and also reducing the manufacturing difficulty of the black matrix (BM) and color filter (CF). At the same time, improving the utilization rate of blue light can improve color conversion efficiency, reduce packaging difficulty, and improve weather resistance.

[0004] Currently, common methods for patterning quantum dots include inkjet printing, nanoimprinting, and photolithography. However, nanoimprinting cannot produce thick QD films, and the QD layer cannot achieve high blue light absorption within the thickness achievable by nanoimprinting technology. Furthermore, nanoimprinting is not conducive to large-scale production, and therefore is rarely used in QD color conversion technology for Micro LEDs. Currently available QD inks suitable for inkjet printing and QD photoresists suitable for photolithography both suffer from low blue light absorption efficiency (OD) per unit thickness, limiting the application of QD in full-color Micro LED displays.

[0005] Traditional quantum dot photoresists mix quantum dots with transparent photoresist, utilizing the photosensitivity of the transparent photoresist to pattern the quantum dots. The advantage of this method is that as long as the quantum dots are uniformly dispersed within the photoresist system, a high-performance quantum dot photoresist can be obtained. However, this method has the following drawbacks: (1) Traditional high-brightness quantum dots can usually be well dispersed in low-polarity solvent systems such as toluene and n-octane, while most photoresists are PGMEA (propylene glycol methyl ether acetate) systems. It is technically difficult to uniformly disperse quantum dots in these systems. (2) In order to achieve uniform dispersion of quantum dots in photoresist, it is necessary to modify or exchange the ligands on the surface of the quantum dots. This step increases the difficulty of the process and will also reduce the PLQY (photoluminescence quantum yield) of the quantum dots, resulting in a decrease in the light conversion efficiency of the quantum dot photoresist. (3) After exposure, the photoresist will form a mesh-like structure. After exposure, the quantum dot photoresist formed by mixing quantum dots will form a state similar to "flour in a sieve". Since quantum dots are not resistant to water and oxygen, when they encounter water and oxygen in the air, problems such as quantum dots escaping from the photoresist and quenching will occur. (4) In order to improve the blue light absorption efficiency of quantum dot photoresist, scattering particles are usually introduced into the quantum dot photoresist, which will reduce the solid content of quantum dots in the photoresist and decrease the blue light absorption efficiency. (5) When exposed, UV light is scattered by scattering particles, resulting in a decrease in photolithography accuracy and burrs on the edge of the pattern. (6) UV light is difficult to reach the bottom of the photoresist, and the film will fall off during development. Summary of the Invention

[0006] This invention aims to overcome the problems of reduced PLQY caused by mixing quantum dots and photoresist in existing quantum dot photoresists, and the poor resistance of quantum dot photoresists to water and oxygen. It provides a high-resolution quantum dot photoresist for the color conversion layer of MicroLEDs, its preparation method, and a full-color MicroLED display chip. The quantum dot photoresist provided by this invention exhibits high PLQY and excellent weather resistance.

[0007] To achieve the above objectives, the first aspect of the present invention provides a quantum dot photoresist, wherein the raw materials for preparing the quantum dot photoresist include functional components and optionally a solvent, and based on the total amount of the raw materials, the amount of the functional components is 20-100 wt.%, and the functional components include quantum dots, multifunctional monomers, monofunctional monomers, binders, initiators, leveling agents, thickeners, and tackifiers; The multifunctional monomer is selected from acrylic acid and at least one compound with the following structural formula: , , , ; The monofunctional monomer is selected from at least one compound with the following structural formulas: , , , ; Among them, R1, R2, R5, R6, R9, R 11 They are independently -CH2-, C4H9-, CH2=CH-CH2-, and C8H 17 -、C 10 H 21 - or C6H5-; R3, R4, R7, and R8 are each independently an alkane, alkene, or aliphatic hydrocarbon with no more than 10 carbon atoms; R 10 It is H, an alkane, alkene, or aliphatic with no more than 10 carbon atoms; n1, n2, and n4 are independently 2-4, and 2≤n3≤6.

[0008] A second aspect of the present invention provides a method for preparing the quantum dot photoresist described in the first aspect of the present invention, wherein the preparation method includes: Quantum dots, multifunctional monomers, monofunctional monomers, and optionally a solvent are mixed to obtain a first mixture; An initiator and a binder are added to the first mixture and mixed evenly under yellow light or dark conditions to obtain a second mixture; Add leveling agent, thickener and viscous agent to the second mixture and mix evenly to obtain quantum dot photoresist.

[0009] A third aspect of the present invention provides a full-color Micro LED display chip, wherein the display chip includes the quantum dot photoresist described in the first aspect of the present invention. Attached Figure Description

[0010] Figure 1 A structural comparison diagram of photoresist prepared by conventional methods and photoresist prepared in this application; Figure 2 The image shows the weather resistance test results of the photoresist prepared in Example 1. Figure 3 This is a process flow diagram of Example I; Figure 4 This is a schematic diagram showing the distribution of red, green, and blue pixel areas in a full-color Micro LED display chip. Detailed Implementation

[0011] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] Furthermore, the term "and / or" in the specification and claims is used to describe the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0014] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0015] The first aspect of the present invention provides a quantum dot photoresist, wherein the raw materials for preparing the quantum dot photoresist include functional components and optionally a solvent, and based on the total amount of the raw materials, the amount of the functional components is 20-100 wt.%, and the functional components include quantum dots, multifunctional monomers, monofunctional monomers, linkers, initiators, leveling agents, thickeners and tackifiers; The multifunctional monomer is selected from at least one compound containing acrylic acid and the following structural formulas: , , , ; The monofunctional monomer is selected from at least one compound with the following structural formulas: , , , ; Among them, R1, R2, R5, R6, R9, R 11 They are independently -CH2-, C4H9-, CH2=CH-CH2-, and C8H17 -、C 10 H 21 - or C6H5-; R3, R4, R7, and R8 are each independently an alkane, alkene, or aliphatic hydrocarbon with no more than 10 carbon atoms; R 10 It is H, an alkane, alkene, or aliphatic with no more than 10 carbon atoms; n1, n2, and n4 are independently 2-4, and 2≤n3≤6.

[0016] The multifunctional monomers and monofunctional monomers selected in this invention both have epoxy structures. By selecting multifunctional monomer molecules with alkyl chains of a certain length as the main body for crosslinking initiated in the photosensitive system, and then adding specific monofunctional molecules, the peeling phenomenon caused by excessive shrinkage during the exposure process and post-baking can be effectively prevented.

[0017] Based on the total amount of raw materials, the amount of functional components can be 20wt.%, 30wt.%, 40wt.%, 45wt.%, 50wt.%, 55wt.%, 60wt.%, 70wt.%, 80wt.%, 90wt.%, 100wt.%, or any value between any two of these. When the proportion of functional components reaches 100wt.%, that is, no solvent is added, then liquid monofunctional monomers can be selected as the dispersion solvent for the entire system.

[0018] Preferably, the alkane includes straight-chain alkanes and branched-chain alkanes.

[0019] Preferably, R3, R4, R7, R8 and R 10 Each can be independently C2H5-, C4H9-, or C8H 17 -

[0020] Preferably, the multifunctional monomer is selected from one or more of pentaerythritol tetraglycidyl ether, pentaerythritol tetraacrylate, glycerol glycidyl ether, and pentaerythritol triacrylate. When the functional monomer is selected from one or more of the above, the exposure metering can be as low as 100 mJ, while the resolution can still reach a linewidth of 2 μm.

[0021] The structural formula of pentaerythritol tetraglycidyl ether is:

[0022] The structural formula of pentaerythritol tetraacrylate is:

[0023] The structural formula of glycerol glycidyl ether is:

[0024] The structural formula of pentaerythritol triacrylate is:

[0025] Preferably, based on the total amount of the functional components, the amount of quantum dots is 20-80 wt.%, the amount of multifunctional monomers is 5-35 wt.%, the amount of monofunctional monomers is 5-15 wt.%, the amount of binder is 0.001-5 wt.%, the amount of initiator is 0.2-10 wt.%, the amount of leveling agent is 0.1-10 wt.%, the amount of thickener is 0.1-10 wt.%, and the amount of tackifier is 0.1-10 wt. Based on the total amount of functional components, the amount of quantum dots can be 20 wt.%, 30 wt.%, 40 wt.%, 50 wt.%, 60 wt.%, 70 wt.%, 80 wt.%, or any value between any two of these. The amount of multifunctional monomers can be 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, or any value between any two of these. The amount of monofunctional monomers can be 5 wt.%, 7 wt.%, 10 wt.%, 12 wt.%, 15 wt.%, or any value between any two of these. The amount of linker can be 0.001 wt.%, 0.005 wt.%, or any value between these. The amounts of initiator can be 0.2wt.%, 0.5wt.%, 1wt.%, 3wt.%, 4wt.%, 5wt.%, and any value between any two of them. The amounts of leveling agent, thickener, and tackifier can be 0.1wt.%, 0.5wt.%, 1wt.%, 3wt.%, 5wt.%, 7wt.%, 10wt.%, and any value between any two of them.

[0026] Preferably, the linker has a functional group that can react with the polyfunctional monomer or the monofunctional monomer, the functional group being selected from one or more of amide, carbamate, carboxyl and hydroxyl groups.

[0027] Preferably, the weight-average molecular weight of the binder is 500-100,000. For example, it can be 500, 800, 1000, 5000, 10000, 50000, 100000, or any value between any two of these numbers.

[0028] This invention selects a chain-like polymer containing more hydrogen bonds as a linker to connect the quantum dot surface ligands and the epoxy photosensitive system. After stirring, the quantum dots are tightly connected to the photoresist network structure in the photoresist solution, thereby improving the stability of the quantum dots.

[0029] Preferably, the binder is selected from one or more of the following: hexamethylene adipamide, poly(p-phenylene terephthalamide), polytetrahydrofuran, polycaprolactone diol, polyacrylic acid, polymethyl polyacrylic acid, polyvinyl alcohol, polyimide, and polyvinylpyrrolidone.

[0030] Polyhexamethylene adipamide and poly(p-phenylene terephthalamide) are chain structures with amide groups. The amide group contains a -CO-NH- structure, where NH is a strong hydrogen bond donor and C=O is a strong hydrogen bond acceptor, allowing perfect bidirectional hydrogen bonds to form within the same group.

[0031] Polytetrahydrofuran and polycaprolactone diol are chain structures with urethane groups. The urethane group -NH-CO-O- is the core functional group of polyurethane, which forms hydrogen bonds with the ether bonds -O- in the chain segment through NH…O=C and NH…O-:NH.

[0032] Polyacrylic acid and polymethyl polyacrylic acid are chain structures with carboxyl groups, polyvinyl alcohol is a chain structure with hydroxyl groups, while polyimide and polyvinylpyrrolidone are chain structures with mixed groups.

[0033] Preferably, the initiator comprises onium salts and / or diazonium salts. Onium salts and diazonium salts can generate superprotic acids under UV light, thereby initiating the polymerization reaction. Onium salts include iodonium salts and thionium salts, with the general formula: (Iodonium salt) or (thionium salts), among which , and Each of these can be an aromatic group (such as benzene ring, naphthalene, pyridine, pyrrole, methylbenzene, etc.). It is a large anion with extremely weak nucleophilicity. The general formula for diazonium salts is... Ar represents an aromatic group (such as a benzene ring), which can be the benzene ring itself or a benzene ring with substituents (such as alkoxy, halogen, or alkyl groups), used to adjust its photolysis stability and absorption wavelength. It is a diazonium cation. It is an anion. As a cationic initiator, It must be a large anion with extremely weak nucleophilicity to ensure that the resulting orthoacid (HX) has sufficient strength. Common anions include: (Tetrafluoroborate) (Hexafluorophosphate) (Hexafluoroarsenate) (Hexafluoroantimonate), etc. Onium salts and diazonium salts are both commercially available.

[0034] Preferably, the onium salt is selected from one or more of diphenyliodonium hexafluorophosphate, (4-octoxyphenyl)phenyliodonium hexafluoroantimonate, (4-dodecylphenyl)phenyliodonium hexafluoroantimonate, bis(4-tert-butylphenyl)iodonium hexafluoroantimonate, triphenylthionium hexafluoroantimonate, (4-phenylthiophenyl)diphenylthionium hexafluoroantimonate, and bis[4-(diphenylsulfonium)phenyl]sulfide-bis-hexafluoroantimonate; The diazonium salt is selected from one or more of phenyldiazotetrafluoroborate, p-methoxyphenyldiazohexafluorophosphate, 2,5-diethoxy-4-morpholinophenyldiazohexafluoroantimonate, and p-chlorophenyldiazohexafluoroarsenate.

[0035] In this invention, the CAS number of diphenyliodonium hexafluorophosphate is 58109-40-3, the CAS number of (4-octyloxyphenyl)phenyliodonium hexafluoroantimonate is 121239-75-6, the CAS number of (4-dodecylphenyl)phenyliodonium hexafluoroantimonate is 71786-70-4, the CAS number of bis(4-tert-butylphenyl)iodonium hexafluoroantimonate is 61358-23-4, the CAS number of triphenylthionium hexafluoroantimonate is 57840-38-7, the CAS number of (4-phenylthiophenyl)diphenylthionium hexafluoroantimonate is 71449-78-0, and the CAS number of bis[4-(diphenylsulfonium)phenyl]sulfide-bis-hexafluoroantimonate is 89452-37-9.

[0036] The CAS number for phenyldiazotetrafluoroborate is 369-57-3, for p-methoxyphenyldiazohexafluorophosphate is 1514-52-9, for 2,5-diethoxy-4-morpholinophenyldiazohexafluoroantimonate is 68413-64-9, and for p-chlorophenyldiazohexafluoroarsenate is 62613-15-4.

[0037] Preferably, the quantum dots are selected from one or more of the following: CdZnSeS / ZnS, CdS, CdSe, CdTe, CdZnSeS, ZnSeS, ZnS, ZnSe, ZnTe, PbS, PbSe, PbTe, HgS, HgSe, HgTe, GaN, GaP, GaAs, InP, InAs, ZnO, SnO2, TiO2, In2O3, Ga2O3, SiO2, NiO, MoO3, WO3, Cu2O, CuO, Fe3O4, Au, Ag, carbon dots, CsPbCl3, CsPbBr3, CsPbI3, CH3NH3PbCl3, CH3NH3PbBr3, and CH3NH3PbI3. This invention does not particularly limit the type of quantum dots; any commonly used ones in the art are acceptable. All quantum dots in this invention can be obtained commercially, or they can be made in-house using common preparation methods in the field. This is prior art and will not be elaborated here.

[0038] In this invention, there are no special requirements for leveling agents, thickeners, tackifiers, etc. Commonly used in the field are all acceptable. Generally speaking, small-molecule leveling agents, thickeners, and tackifiers can be selected to improve the flatness, thickness, and adhesion between the photoresist and the substrate after spin coating.

[0039] Leveling agents can be silicone-based (such as dimethylsiloxane, BYK-301, Tego-410), acrylate-based (such as BYK-354, EFKA-3777), fluorocarbon-based (such as BYK-380N, Tego-2700), etc. Thickeners can be associative polyurethanes (such as ASE-60, 2020 / 2025PUR), cellulose-based (such as sodium carboxymethyl cellulose, LH-100M, Benecel series), polyacrylic acid-based (such as TT-935, ASE-60), inorganic-based (such as bentonite, nano-montmorillonite), etc. Tackifiers can be rosin resin, petroleum resin, phenolic resin, silicone-based (such as KH560 silane coupling agent), etc.

[0040] A second aspect of the present invention provides a method for preparing the quantum dot photoresist described in the first aspect of the present invention, wherein the preparation method includes: Quantum dots, multifunctional monomers, monofunctional monomers, and optionally a solvent are mixed to obtain a first mixture; An initiator and a binder are added to the first mixture and mixed evenly under yellow light or dark conditions to obtain a second mixture; Add leveling agent, thickener and viscous agent to the second mixture and mix evenly to obtain quantum dot photoresist.

[0041] Preferably, the preparation method further includes spin-coating and baking the quantum dot photoresist, followed by exposure and development. The exposure dose is 50-10000 mJ, and the development time is 30-180 s. The exposure dose can be any value between any two of the following: 50 mJ, 100 mJ, 150 mJ, 200 mJ, 400 mJ, 600 mJ, 800 mJ, 1000 mJ, 5000 mJ, 10000 mJ, and any value between any two of them. The development time can be any value between any two of the following: 30 s, 40 s, 50 s, 80 s, 100 s, 150 s, 180 s.

[0042] Preferably, the preparation method further includes adding dichloromethane to the second mixture to disperse the initiator evenly, and then adding the leveling agent, thickener and viscous agent.

[0043] In photoresists prepared using traditional methods, the quantum dots are typically directly incorporated into the colloid and have no connection to the network structure formed by the photosensitive monomers. Figure 1As shown, the photoresist prepared by this invention has a network structure, in which quantum dots are connected to photosensitive monomers (multifunctional monomers and monofunctional monomers) through a linker, which effectively improves the stability of quantum dots.

[0044] The quantum dot photoresist prepared by this invention has a blue light absorption rate of up to 99%, a PLQY of over 90%, and no peeling.

[0045] A third aspect of the present invention provides a full-color Micro LED display chip, wherein the display chip includes the quantum dot photoresist described in the first aspect of the present invention.

[0046] Preferably, the display chip includes: The blue pixel area is provided with blue light by direct emission from the blue light epitaxial layer; The red pixel area is filled with red quantum dot photoresist, which receives blue light emitted by the blue epitaxial layer and emits red light after photoluminescence. The green pixel area is filled with green quantum dot photoresist, which receives blue light emitted from the blue epitaxial layer and emits green light after photoluminescence.

[0047] Preferably, the full-color Micro LED display chip includes a driving layer, on which there are frustum-shaped pixel stands corresponding to its P-pole, and there are grooves between adjacent pixel stands; The pixel stage includes an ITO layer, a first semiconductor layer, a blue light multi-quantum well layer, and a second semiconductor layer, which are arranged layer by layer from the driving layer upwards. The sidewalls of the pixel stage and the driving layers between adjacent pixel stages are covered with a first insulating layer. All surfaces of the first insulating layer and the top surface of the pixel stage are covered with the same conductive layer, which is connected to the N-terminal of the driving layer. The surface of the conductive layer is covered with a second insulating layer. Metal baffles are provided in the grooves between adjacent pixel stations, and the metal baffles around the same pixel station form a filling groove. The filling groove is filled with red quantum dot photoresist, green quantum dot photoresist or transparent photoresist, thereby forming corresponding red pixel areas, green pixel areas or blue pixel areas.

[0048] The pixel array is typically arranged in an array. After filling with the corresponding photoresist, the red, green, and blue pixel areas are alternately distributed in both horizontal and vertical directions, as shown below. Figure 4 As shown.

[0049] The first semiconductor layer is generally a P-GaN layer, the second semiconductor layer is generally an N-GaN layer, and the conductive layer can generally be a TiAlTi composite conductive layer. These are all existing technologies in this field and will not be elaborated here.

[0050] Preferably, the metal barrier is trapezoidal in shape, with its larger end close to the second insulating layer. When the quantum dot photoresist is excited, it emits light in all directions. Lateral emission can cause crosstalk, so a barrier structure is needed to separate adjacent pixels. Metal is reflective, and by setting the barrier in a trapezoidal shape, some light can propagate towards the light-emitting side through multiple reflections, thereby improving the light emission intensity.

[0051] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the test methods and testing equipment used in the following embodiments are conventional test methods and testing equipment in the art.

[0052] Polymethacrylic acid was purchased from Adamas, with a weight-average molecular weight of approximately 80,000. Polyhexamethylene adipamide was purchased from Adamas, with a weight-average molecular weight of approximately 15,000. Polytetrahydrofuran was purchased from Adamas, with a weight-average molecular weight of approximately 650.

[0053] Preparation Example 1 Synthesis of quantum dots: CdZnSeS / ZnS nanocrystals Dissolve 5 mmol of selenium (Se) powder and 5 mmol of sulfur (S) powder in 5 mL of trioctylphosphine (TOP) to obtain... Precursor solution.

[0054] 0.14 mmol of cadmium acetate, 3.41 mmol of zinc oxide, and 7 ml of oleic acid ligand were placed in a 50 ml three-necked flask. Under nitrogen protection, the reaction mixture in the flask was heated to 150 °C and maintained for 30 min to remove acetic acid and water from the reaction mixture. Then, 15 ml of octadecene (… After adding ODE to the three-necked flask, the reaction system was heated to 310°C, and then 2 ml of [unspecified substance] was injected into the reaction system. The precursor solution was cooled to 300°C and the reaction was continued for 15 minutes, which resulted in the formation of CdZnSeS / ZnS nanocrystal particles composed of CdZnSeS / ZnS nanocrystals and oleic acid ligands. The CdZnSeS / ZnS nanocrystals have a core-shell structure with CdZnSeS as the core and ZnS as the shell.

[0055] An excess of a mixed solution of methanol and acetone was added to the reaction system to precipitate carbon quantum dots. The volume ratio of methanol to acetone in the mixed solution was 3:1. The mixture was centrifuged at 8000 rpm for 5 min to obtain CdZnSeS / ZnS nanocrystalline particles. This process was repeated at least once: the precipitate was dissolved in 5 ml of octane solution, 15 ml of acetone was added, and the mixture was centrifuged at 8000 rpm for 5 min to obtain CdZnSeS / ZnS nanocrystalline particles.

[0056] The CdZnSeS / ZnS nanocrystals synthesized by the above method have a particle size of approximately 6 nm and can produce green light after an electric potential is applied.

[0057] By changing the reaction temperature, reaction time, material ratio, and number of surface ligands during the synthesis process, the size of CdZnSeS / ZnS nanocrystals can be altered, thereby enabling the CdZnSeS / ZnS nanocrystals to produce light of other colors after an electric potential is applied.

[0058] Preparation Example 2 The procedure was carried out in accordance with Preparation Example 1, the only difference being: the injected... The precursor solution was 3 ml, and the reaction time was extended to 25 minutes after injection.

[0059] The CdZnSeS / ZnS nanocrystals synthesized by the above method have a particle size of 9 nm and can produce red light after an electric potential is applied.

[0060] Example 1 S1 Dissolve the green quantum dots from Preparation Example 1 in toluene to obtain a toluene solution of 500 mg / mL green quantum dots; S2 Take 1 mL of quantum dot toluene solution, add 0.3 g of ethylene glycol glycidyl ether and 0.1 g of butyl glycidyl ether to it, stir overnight and mix thoroughly; Structural formula of ethylene glycol glycidyl ether:

[0061] Butyl glycidyl ether structural formula:

[0062] S3 Add 2 mg of diphenyliodonium hexafluorophosphate (CAS No. 58109-40-3) as a photoinitiator and 0.05 mg of polymethacrylic acid (to form hydrogen bonds) as a linker to the S2 solution, and stir thoroughly in the dark. S4 Add 100 μL of dichloromethane to the S3 solution to help disperse the photoinitiator and adjust the solution polarity; S5. Add 10 mg of dimethylsiloxane, 10 mg of sodium carboxymethyl cellulose, and 2 mg of KH560 silane coupling agent to the S4 solution as leveling agent, thickener, and viscous agent, respectively, and stir thoroughly to obtain a high-efficiency green quantum dot photoresist (G-QDPR).

[0063] Excitation was performed using 460 nm blue light (the emission wavelength is determined by the quantum dots incorporated therein; after the photoresist is prepared, the wavelength shift is < ±5 nm), and the PLQY of the photoresist solution was tested to be 96%.

[0064] S6 spin-coated G-QDPR onto a transparent glass substrate with a coating thickness of approximately 2 μm. The absorbance at 460 nm was 2, indicating a blue light absorption rate of 99% at 460 nm. The PLQY of the spin-coated quantum dot photoresist film was 94%. S7 Bake the S6 spin-coated film at 80°C for 30 min (soft bake). S8 was exposed using a stepper lithography machine with an exposure dose of 800mJ and developed with a developer for 45s to obtain a patterned quantum dot pixel array. The pixels were square with a side length of 5 μm and a spacing of 5 μm. S9 is baked at 140℃ for 30 minutes (hard bake) to completely cure the QD layer; S10 Prepare red CdZnSeS / ZnS quantum dot photoresist (R-QDPR) according to S1-S9, wherein the red CdZnSeS / ZnS quantum dots are from preparation example 2, and overlay G-QDPR and R-QDPR are performed and developed to obtain patterned quantum dot color conversion films with red and green colors. Overlay and development are existing technologies in the field and will not be described again. After bonding the prepared red and green quantum dot color conversion film with the inverted vertical structure blue Micro LED micro-display module, a QDCC Micro LED module with full-color red, green and blue display can be obtained.

[0065] To test the durability of the quantum dot photoresist prepared in this embodiment, the following tests were further performed: The photoresist after spin coating in step S7 was exposed at 365nm for 1000mJ, and then cured at 140℃ for 30min to obtain a cured quantum dot photoresist film. The PLQY (0h) of the cured quantum dot photoresist film was then measured. The cured quantum dot photoresist film was then placed in a dual 85 aging chamber (temperature 85℃, humidity 85%). PLQY was measured every 24 hours for the first 240 hours, and every 72 hours thereafter. Using the PLQY measured at 0h as a baseline, the PLQY retention rate was calculated (PLQY retention rate = PLQYnh / PLQY0h). The change in PLQY retention rate is shown below. Figure 2 As shown, the quantum dot photoresist prepared by this invention can still maintain more than 98% of PLQY after 1300 hours of aging with dual 85, which shows that it has good weather resistance.

[0066] Example 2 The procedure was carried out in accordance with Example 1, except that the multifunctional monomer was acrylic acid.

[0067] The prepared quantum dot photoresist was excited using 460 nm blue light, and the PLQY of the photoresist solution was tested to be 92%.

[0068] The quantum dot photoresist prepared in this embodiment was spin-coated onto a transparent glass substrate. The spin-coating thickness was approximately 2 μm. The absorbance at 460 nm was 2.1, which means that the blue light absorption rate at 460 nm was 99.2%. The PLQY of the quantum dot photoresist film after spin-coating was 89%.

[0069] Example 3 The procedure was carried out as in Example 1, except that ethylene glycol glycidyl ether was replaced with pentaerythritol tetraglycidyl ether. As a result, the exposure dose in S8 can be as low as 100 mJ, yielding a patterned quantum dot pixel array with square pixels, each pixel having a side length of 2 μm and a spacing of 2 μm. This provides a higher resolution than that of Example 1.

[0070] Example 4 The procedure is the same as in Example 1, with the only difference being: Replace ethylene glycol glycidyl ether with R2 is CH2=CH-CH2, and n2 is 4; Replace butyl glycidyl ether with R6 is C 10 H 21 .

[0071] Furthermore, quantum dots are directly dissolved in monofunctional monomers, eliminating the need to add toluene and dichloromethane during the preparation process.

[0072] Example 5 The procedure is the same as in Example 1, with the only difference being: Replace ethylene glycol glycidyl ether with In this case, R3 and R4 are both C2H5, and n3 is 5; Replace butyl glycidyl ether with , where R7 and R8 are both C4H9.

[0073] Example 6 The procedure was carried out in accordance with Example 1, except that 500 mg of quantum dots were dissolved in 2.5 mL of toluene to obtain a toluene solution containing quantum dots, and then all of the toluene solution containing quantum dots was used in subsequent steps S2-S6 (the functional components in the raw materials accounted for 29%).

[0074] Example 7 The procedure is the same as in Example 1, with the only difference being: In step S1, the concentration of the toluene solution containing green quantum dots is 800 gm / mL; In step S2, the amount of ethylene glycol glycidyl ether is 0.4 g.

[0075] Example 8 The procedure is the same as in Example 1, with the only difference being: In step S2, the amount of ethylene glycol glycidyl ether is 0.1 g.

[0076] Example 9 The procedure is the same as in Example 1, with the only difference being: The binder in step S3 is 5 mg of polyhexamethylene adipamide.

[0077] Example 10 The procedure is the same as in Example 1, with the only difference being: In step S3, the binder is 30 mg of polytetrahydrofuran.

[0078] The PLQY and weather resistance of the photoresist before and after spin coating were tested using the same method as in Example 1. Except for Example 3, the photoresists prepared in other examples were exposed and developed using the same method as in Example 1, and the resolution of the pixels was measured. The results of the above tests are shown in Table 1.

[0079] Table 1

[0080] Comparative Example 1 The procedure was carried out in accordance with Example 1, except that the ethylene glycol glycidyl ether in Example 1 was replaced with epoxy resin DGEBA (bisphenol A diglycidyl ether, CAS No. 1675-54-3), while the other proportions remained unchanged.

[0081] After exposure and development, the minimum photolithography resolution can only reach a linewidth of 100μm; smaller patterns will show adjacent patterns sticking together. Furthermore, the unexposed areas are difficult to develop, and the development time is extended to 10 minutes before the pattern begins to appear. Continuing to extend the development time will result in a large amount of peeling on the pattern on the wafer.

[0082] Comparative Example 2 The procedure was performed as described in Example 1, except that no binder was added, while the other proportions remained the same. Within 3 seconds of immersion in the developer, the front-side pattern began to peel off, making it impossible to produce a valid photolithographic pattern.

[0083] In addition, this application also provides embodiments of the method for preparing a full-color Micro LED display chip.

[0084] Example I Full-color Micro LED display chips, such as Figure 3 As shown, the preparation method is as follows: S1 Bonding: A metal layer is deposited on the wafer surfaces of a blue light-emitting epitaxial wafer (including ITO layer 2, P-GaN layer 3, B-MQW layer 4, N-GaN layer 5, U-GaN layer, and substrate layer) with an emission wavelength of 460±5nm, and the driver chip 1 (IC chip with an array of P-polarities and an outer N-polarity) using electron beam vacuum deposition. The two layers are then metal-bonded using wafer-level bonding equipment (typically Au-Au or Au-Sn bonding), so that the driver chip 1 is composited onto the ITO layer 2 of the blue light-emitting epitaxial wafer. Figure 3 The first row, number 1 is shown in the figure.

[0085] S2 Substrate Removal: The substrate of the blue epitaxial wafer is polished, and then the sapphire substrate of the blue epitaxial wafer is removed using a laser lift-off device, leaving only ITO layer 2, P-GaN layer 3, B-MQW layer 4, and N-GaN layer 5 (the ITO layer serves to spread the current, and the remaining P-GaN layer 3, B-MQW layer 4, and N-GaN layer 5 become the blue epitaxial layer). Figure 3 The second image in the first row shows the process of polishing. The purpose of polishing is to allow the laser to penetrate to a predetermined depth.

[0086] S3 Pixel Structure: A frustum structure is etched onto the p-polarity of the IC chip using a photoresist mask (usually a positive photoresist, such as commercially available AZ series, SU8 series, 703 series, etc.). This frustum serves as the pixel platform for the Micro LED display chip, and its shape is as follows: Figure 3 The last image in the first row.

[0087] S4 Cutting the P electrode: Etching away the ITO layer within the pixel channel (e.g.) Figure 3 (as shown in the last figure of the first row), so that the P electrodes of all pixels are separated.

[0088] S5 First insulating layer: An insulating SiO2 layer is deposited on the side surface, top surface, and trench 11 between adjacent pixel stations using PECVD. A photoresist layer is then applied as a mask layer to the area except the top surface of the pixel station using photolithography. The SiO2 on the top surface of the pixel station is removed by ICP etching to form the first insulating layer 6. The function of the first insulating layer 6 is to prevent short circuit caused by connecting the N-electrode and P-electrode during N-electrode fabrication.

[0089] S6 N electrode: A TiAlTi composite conductive layer 7 is deposited on the surface of the process plane using an electron beam vacuum coating device, serving as the N electrode of each pixel. The composite conductive layer 7 covers the surface of the first insulating layer 6, the top surface of the pixel stage, and the trench 11 between adjacent pixel stages, and its bottom is connected to the N pole of the IC chip.

[0090] S7 Second insulating layer: A layer of SiO2 is deposited on the composite conductive layer 7 using PECVD to form a second insulating layer 8. The function of this layer is to prevent the quantum dot photoresist from being connected by the metal barrier during the preparation of the metal barrier.

[0091] S8 Metal Barrier: A layer of Al is deposited on the surface using an electron beam vacuum deposition system. After passing through a photoresist mask, an ICP etching process is used to form a metal barrier 9 in the trench 11 between the pixel cells. Figure 3 As shown in the first image of the third row, the metal retaining walls 9 around the pixel platform enclose and form the filling groove 10.

[0092] S9 Filling with quantum dot photoresist: Using the quantum dot photoresist prepared in Example 1 above, red and green quantum dot photoresist are filled into the filling groove 10 at a preset position to form corresponding red and green pixel areas. Blank photoresist is then used to fill the filling groove 10 at the preset position to form blue pixel areas. The final distribution of the red, green, and blue pixel areas can be as follows: Figure 4 As shown (of course, the color pixels can also be distributed in the corresponding areas according to the pattern shape to be displayed).

[0093] S10 Packaging: A transparent substrate (such as glass) in the visible light band is covered in all filling slots 10 to encapsulate the chip, prevent moisture and oxygen from attacking the quantum dots, and improve the stability of the chip.

[0094] The full-color Micro LED display chip thus obtained includes: a driving layer 1 (IC chip), on which there are pre-distributed P poles and N poles, and on which there are frustum-shaped pixel stations corresponding to its P poles, and there are grooves 11 between adjacent pixel stations. The pixel stage includes an ITO layer 2, a first semiconductor layer 3 (i.e., a P-GaN layer), a blue light multiple quantum well layer 4 (B-MQW layer), and a second semiconductor layer 5 (N-GaN layer) arranged layer by layer from the driving layer 1 upwards. The ITO layer 2 is bonded to the P-terminal of the driving layer 1 and is conductive. The sidewalls of the pixel stage and the driving layer 1 between adjacent pixel stages are covered with a first insulating layer 6 (SiO2 layer). The top surface of the pixel stage and all surfaces of the first insulating layer 6 are covered with the same conductive layer 7, which is conductive to the N-terminal of the driving layer 1. The surface of the conductive layer 7 is covered with a second insulating layer 8. A metal barrier 9 (Al material) is provided in the groove 11 between adjacent pixel stations. The metal barrier 9 is preferably trapezoidal. The metal barrier 9 around the same pixel station forms a filling groove 10. The filling groove 10 is filled with red quantum dot photoresist, green quantum dot photoresist or transparent photoresist, thereby forming a corresponding red pixel area, green pixel area or blue pixel area.

[0095] The light-emitting principle of the chip fabricated in this example is as follows: After power is supplied, holes generated by P-GaN and electrons generated by N-GaN recombine in the blue multi-quantum well layer (B-MQW layer) to emit blue light. In the blue pixel area, because it is filled with transparent photoresist, the emitted blue light is directly emitted and displayed as blue. Similarly, in the red and green pixel areas, holes and electrons of P-GaN and N-GaN recombine in the MQW layer to emit blue light. This blue light then excites the corresponding quantum dot photoresist to emit the corresponding red and green light, thus making the corresponding areas appear red and green.

[0096] The contents not described in detail in this specification are existing technologies known to those skilled in the art, and will not be elaborated upon here.

[0097] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A quantum dot photoresist, characterized in that, The raw materials for preparing the quantum dot photoresist include functional components and optionally solvents. Based on the total amount of the raw materials, the amount of the functional components is 20-100 wt.%, and the functional components include quantum dots, multifunctional monomers, monofunctional monomers, binders, initiators, leveling agents, thickeners, and tackifiers. The multifunctional monomer is selected from at least one compound containing acrylic acid and the following structural formulas: 、 、 、 ； The monofunctional monomer is selected from at least one compound with the following structural formulas: 、 、 、 ； Among them, R1, R2, R5, R6, R9, R 11 They are independently -CH2-, C4H9-, CH2=CH-CH2-, and C8H 17 -、C 10 H 21 - or C6H5-; R3, R4, R7, and R8 are each independently an alkane, alkene, or aliphatic hydrocarbon with no more than 10 carbon atoms; R 10 It is H, an alkane, alkene, or aliphatic with no more than 10 carbon atoms; n1, n2, and n4 are independently 2-4, and 2≤n3≤6.

2. The quantum dot photoresist according to claim 1, wherein, The alkanes include straight-chain alkanes and branched-chain alkanes; Preferably, R3, R4, R7, R8 and R 10 Each can be independently C2H5-, C4H9-, or C8H 17 -; Preferably, the multifunctional monomer is selected from one or more of pentaerythritol tetraglycidyl ether, pentaerythritol tetraacrylate, glycerol glycidyl ether, and pentaerythritol triacrylate.

3. The quantum dot photoresist according to claim 1 or 2, wherein, Based on the total amount of the functional components, the amount of quantum dots is 20-80 wt.%, the amount of multifunctional monomers is 5-35 wt.%, the amount of monofunctional monomers is 5-15 wt.%, the amount of binder is 0.001-5 wt.%, the amount of initiator is 0.2-10 wt.%, the amount of leveling agent is 0.1-10 wt.%, the amount of thickener is 0.1-10 wt.%, and the amount of tackifier is 0.1-10 wt.

4. The quantum dot photoresist according to claim 3, wherein, The linker has a functional group that can react with the multifunctional monomer and the monofunctional monomer, the functional group being selected from one or more of amide group, carbamate group, carboxyl group and hydroxyl group; Preferably, the weight-average molecular weight of the binder is 500-100,000.

5. The quantum dot photoresist according to claim 4, wherein, The binder is selected from one or more of the following: hexamethylene adipamide, poly(p-phenylene terephthalamide), polytetrahydrofuran, polycaprolactone diol, polyacrylic acid, polymethyl polyacrylic acid, polyvinyl alcohol, polyimide, and polyvinylpyrrolidone.

6. The quantum dot photoresist according to claim 3, wherein, The initiator includes onium salts and / or diazonium salts.

7. The quantum dot photoresist according to claim 6, wherein, The onium salt is selected from one or more of the following: diphenyliodonium hexafluorophosphate, (4-octyloxyphenyl)phenyliodonium hexafluoroantimonate, (4-dodecylphenyl)phenyliodonium hexafluoroantimonate, bis(4-tert-butylphenyl)iodonium hexafluoroantimonate, triphenylthionium hexafluoroantimonate, (4-phenylthiophenyl)diphenylthionium hexafluoroantimonate, and bis[4-(diphenylsulfonium)phenyl]sulfide-bis-hexafluoroantimonate. The diazonium salt is selected from one or more of phenyldiazotetrafluoroborate, p-methoxyphenyldiazohexafluorophosphate, 2,5-diethoxy-4-morpholinophenyldiazohexafluoroantimonate, and p-chlorophenyldiazohexafluoroarsenate.

8. The quantum dot photoresist according to any one of claims 4-7, wherein, The quantum dots are selected from one or more of the following: CdZnSeS / ZnS, CdS, CdSe, CdTe, CdZnSeS, ZnSeS, ZnS, ZnSe, ZnTe, PbS, PbSe, PbTe, HgS, HgSe, HgTe, GaN, GaP, GaAs, InP, InAs, ZnO, SnO2, TiO2, In2O3, Ga2O3, SiO2, NiO, MoO3, WO3, Cu2O, CuO, Fe3O4, Au, Ag, carbon dots, CsPbCl3, CsPbBr3, CsPbI3, CH3NH3PbCl3, CH3NH3PbBr3, and CH3NH3PbI3.

9. A method for preparing a quantum dot photoresist according to any one of claims 1-8, characterized in that, The preparation method includes: Quantum dots, multifunctional monomers, monofunctional monomers, and optionally a solvent are mixed to obtain a first mixture; An initiator and a binder are added to the first mixture and mixed evenly under yellow light or dark conditions to obtain a second mixture; Add leveling agent, thickener and viscous agent to the second mixture and mix evenly to obtain quantum dot photoresist.

10. The preparation method according to claim 9, wherein, The preparation method further includes spin-coating and baking the quantum dot photoresist, followed by exposure and development, with an exposure dose of 50-10000mJ and a development time of 30-180s; And / or, the preparation method further includes adding dichloromethane to the second mixture to disperse the initiator evenly, and then adding the leveling agent, thickener and viscous agent.

11. A full-color Micro LED display chip, characterized in that, The display chip includes the quantum dot photoresist according to any one of claims 1-8; Preferably, the display chip includes: The blue pixel area is provided with blue light by direct emission from the blue light epitaxial layer; The red pixel area is filled with red quantum dot photoresist, which receives blue light emitted by the blue epitaxial layer and emits red light after photoluminescence. The green pixel area is filled with green quantum dot photoresist, which receives blue light emitted from the blue epitaxial layer and emits green light after photoluminescence.

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